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Publication
Zeitschrift fur Physikalische Chemie
Paper
Prospects for molecular spectroscopy at high spatial resolution
Abstract
This work discusses the prospects and feasibility of optical spectroscopy and microscopy of single molecules at nanometer resolution via apertureless, antenna-based near-field scanning optical microscopy. First, different near-field optical methods are compared, which detect the weak scattering or fluorescence from a probe-single molecule interaction at high spatial resolution. Specifically, ultimate sensitivities of coherent (bright-field) and non-coherent (dark-field) apertureless near-field microscopes for resonant (e.g., scattering, absorption) and non-resonant (e.g., n-photon fluorescence) imaging applications are discussed and key differences between absorption and scattering/fluorescence methods are elucidated. Secondly, the enhanced near-field interaction between a probe and a luminescent polystyrene nanosphere (doped with fluorescein-like dye) is investigated as a function of the sample size, which reveals a strong probe-induced enhancement of the fluorescence. Finally, the data are used to predict ultimate sensitivities as well as limitations of current apertureless near-field optical techniques. © by Oldenbourg Wissenschaftsverlag, München.